Five Alarm Death March
by Becky Blue Eyes
Summary: Because despite Tadashi being a good person, Hiro is his baby brother, his otouto, and grief can do savage things to the gentle mind. Dark AU, multiple character deaths, implicit gore. SPOILERS FROM BIG HERO 6
1. Five Alarms

**because the best way to come terms with an emotionally compromising movie is to make sad fanfics**

**disclaimer: I don't own the copyrighted material within**

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><p><em>one alarm<em>

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><p>Tadashi smiles at Hiro and it's his big beaming "I'm so proud of you little brother" times twenty because now Hiro's in college, about to change the world with that big brain of his. They're all going to celebrate, Fred already prodding Aunt Cass about what's on the menu for tonight, and Hiro ducks his head when Tadashi speaks into his ear, "You're incredible."<p>

Hiro can be a quiet thing at times, so the grin stretching across his face just lights up Tadashi's world. Hiro straightens up, ears red, and yells, "Wait, gotta get my neutrotransmitter from my display!" and heads back into the building.

Tadashi lets him go, and regrets that when the fire starts. The group's back at the parking lot by this point so he wastes valuable seconds scrambling and vaulting over shellshocked and smokesick people to get at the doors. Men hold him back but he flails out of his grip because his little brother is in there! One of his classmates coughs that Prof. Callaghan is also lost in the fire and part of Tadashi jolts at the idea of both his mentor and his little brother burning to death.

Most of all Hiro, not Hiro, not his little brother, not his otouto; Tadashi rockets up the stairs

and is thrown back by an explosion, glass tearing across his arms and acrid smoke filling his lungs. Tadashi is a native of San Fransokyo and knows how the southern valleys burn in the summer, how his mother uses to set the oven on fire, how cinders crackle in a engineering class bonfire.

This smoke is too sweet, and he screams and screams until people take him away and Baymax asks him on a scale of one to ten how much do you hurt and all is lost.

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><p><em>two alarm<em>

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><p>They decide to bury Hiro's urn by their parents, and Tadashi is thankful that his arms are still bandaged because the idea of passing tiny charcoal bones between chopsticks makes him hurl into the funeral home wastebasket. It rains, and he needs to be strong for Aunt Cass because her wrists are shaking too much to hold up the umbrella, yet he is too busy drowning in his grief.<p>

Hiro is dead.

Hiro is dead.

Tadashi's little baby brother is dead at fourteen and the fire was so intense that hardly anything remained for a proper cremation. It's not like their parents, useless slabs of cold flesh still strapped into twisted car seats. It's not like Prof. Callaghan, who died near the epicenter of the explosion and left behind not a trace.

Hiro was mutilated, Hiro died in agony and Tadashi wishes that he could've died with him.

He doesn't tell Aunt Cass this, nor his friends; he hides it in his side of the room, Hiro's section neatly sectioned off and left to dust over because the idea of changing anything of his little brother's makes Tadashi howl in the shower. His friends surround him, a perpetual honor guard at school where the teachers and the students and the reports look at him with too much pity, and it helps a bit. Honey is nurturing, Gogo is stoic, Wasabi keeps Tadashi straightened up and Fred is so inappropriate that Tadashi can't help but snort sometimes.

But at night he still screams, and wails, and sobs, and Hiro is dead.

What kind of niisan allows this to happen to his otouto? How could Tadashi have let Hiro die?

Baymax is always operational, because no matter how his magnum opus tries, Tadashi can't be satisfied with his care because there's too many shrapnel wounds tearing out chunks shaped like Hiro's name.

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><p><em>three alarm<em>

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><p>Tadashi finds the little microbot twitching by the stairs, and picks it up before Mochi can eat it. He doesn't go to school that day because if he had just taken Hiro to the bot battle, Hiro never would've made that microbot exhibit, and never would've died. Aunt Cass keeps her distance to let him rage at the world, and it's only Baymax's gentle restraint that keeps Tadashi from gashing open his stitches against door frames and table edges.<p>

He cuddles with Baymax and Mochi in the dark, and notices that the microbot wants to go somewhere. Petting Mochi one last time and hugging Aunt Cass to apologize for the noises that disturb her customers, Tadashi and Baymax go on a walk to see where his little brother's microbot wants to be laid to rest.

Tadashi doesn't expect to find a warehouse and thousands of microbots and a man in a Noh mask out for his blood. Hah, the mask matches the antagonist of a kabuki play his father once dragged him and Hiro too, he wondered if Hiro would've confused—

Hiro is dead and his machines are being used by someone Tadashi wouldn't trust as far as Baymax could throw him. The man has the neurotransmitter that Hiro invented and where did he get it from, it was lost in the fire? Did he...set the fire? Did that man take the neurotransmitter, wrestle it from Hiro's hands, steal the microbots, and leave Tadashi's baby brother to die?

For the first time since the fire, Tadashi burns.

He heads home to upgrade Baymax with new moves and objectives incompatible with his nursing chip. Baymax cautions against this, as these martial arts and power blows would cause injury to a human being. Tadashi says that getting the man who murdered his brother would increase his mental and physical health, and Baymax is programmed to drop it.

Just in case, Tadashi puts the new moves on a new black chip and sets it across from the green one, just enough room between the two for an easy removal of either one.

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><p><em>four alarm<em>

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><p>Tadashi finds the man at the docks, and despite Baymax's move upgrades and armor, they are outmatched. Baymax contacts Tadashi's friends and they escape with Gogo's intense driving, and Tadashi really doesn't want to explain to his friends why he was out at midnight against a murderer but Fred's couch is warm and all of their eyes are fixed on him. Hiro once looked at him like that.<p>

"If we don't stop him, Hiro's murderer gets away and who knows what he'll do to the city?" Tadashi convinces them to be on his side, against this monster, this Yokai, who stole away the light in his life to lock it away six feet under. Fred gives Tadashi the idea of a super team, and the group is up for anything to get Tadashi happy again.

Tadashi knows that Hiro could've done this better. Hiro was a better inventor than Tadashi could've dreamed of being, he could've changed the world and Yokai changed that; what once filled him with pride now fills Tadashi with despair. But with his friends' input, Tadashi helps them craft their own weapons and suits. He even laughs when Gogo collides with Baymax and is knocked out of her wheels, and almost feels halfway normal again.

His suit is simple, along the lines of Wasabi's with his weapons being a katana and a pair of daggers. Clean, elegant, surgical, enhanced to never break and be almost as sharp as Wasabi's blades and move so sweetly through the air like Gogo's wheels. Honey giggles that he looks like a samurai, and Tadashi saves his tears for later because that's what he dressed up as with his last Halloween with Hiro.

Outside of his friends' eyes and with only Baymax on standby, Tadashi practices how to tear out a man's throat with a flick of the wrist, how to disembowel him with a quarter turn, how to draw out the cuts long and slow and mutilate Yokai just as Yokai had mutilated Hiro.

Baymax asks, after the fifteenth dummy is discarded, if this is what Hiro would have wanted. Tadashi shuts Baymax down for the night and continues his night time habit of crying himself to sleep.

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><p><em>five alarm<em>

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><p>Baymax finds Yokai on a deserted island after Tadashi sneaks him up onto one of the bridge's support towers. Akuma Island hides the remains of yet another failed Krei invention, and the image of Abigail Callaghan disappearing into the fire turns Tadashi's stomach until he swallows back bile. Hiro would've clicked with Abigail so quickly, had the two been able to meet, yet it seems that Krei (Krei? Did he do this? Was he Yokai? How hard would it be to end his life?) decided to screw both of them over via explosion.<p>

Yokai is there, and the team's teamwork is shoddy but they manage to tear away the mask and

it's Prof. Callaghan

and he doesn't care that when he stole the neurotransmitter from Hiro that he knocked the boy's head against a pillar

he doesn't care that this stunned Hiro so badly that he had to try and crawl out of the fire, over burning glass and burning metal and so much pain

he doesn't care that maybe just maybe if Callaghan hadn't been so hard on Hiro, Hiro could've escaped and Tadashi's little brother wouldn't have died in the fire

Tadashi's great mentor and teacher and confidante and the man he would've trsuted Hiro's academics with doesn't care

and Tadashi tears out Baymax's nurse chip, and helps Baymax chase Callaghan down.

The fight can't be called a fight, not with Baymax throwing aside Honey and Gogo and Wasabi and Fred so that Tadashi can chop off Callaghan's hand. He chops off the other, then he hacks away at the arms and legs, screaming in Japanese about how Hiro's bones were so tiny and misshapen from the fire and how they had to use a child's urn and how Hiro was only fourteen, Tadashi's otouto was only fourteen and the best thing in Tadashi's life and Callaghan murdered him.

Callaghan screeches back about how Krei killed his daughter and nothing could stand in the way, not even the little brother of his prodigy; nothing matters because Callaghan wants his daughter back. Tadashi roars, "I WANT MY LITTLE BROTHER BACK!" and digs his blades into Callaghan's chest.

Honey is hysterical and Wasabi is sick from the gore and Gogo is trying to brace Fred's broken arm because Baymax is too enthusiastic with keeping the four back. Tadashi screams, and wails, and sobs Hiro's name, stabbing downwards over and over to try and kill the demons tormenting his family in the afterlife.

He doesn't notice when Honey manages to put back in Baymax's nursing chip, or when he tore open his newer stitches arching across his breast bone, or when Gogo and Wasabi knock away the swords and drag him away from Callaghan's once-body. His howling is raw and jagged, stripped bare from a throat that once spoke Hiro's name without grief clogging the kanji. He collapses on the ground, clawing at the concrete while Gogo numbly investigates the rest of the security footage and Baymax heals his injures.

"On a scale of one to ten," and Baymax's voice is so soft now, the synthetic tones filled with what Tadashi identifies as disgust. Hiro is dead and Tadashi is a murderer, and Baymax has been violated beyond all measure. Vinyl hands steady Tadashi's heaving shoulders, "How bad is your pain?"

"Ten," Tadashi chokes out, and Hiro has been avenged but now Tadashi is a murderer and when he dies he will never be granted the honor of seeing his brother again. How will he explain this to Aunt Cass, to his friends?

He is left to grieve for the wreckage of his life alone on the blood-splattered floor, while the ghosts of Abigail and Tadashi's parents and maybe even Callaghan look at him in horror, and Hiro—

Hiro is dead, and Tadashi is a murderer, and nothing will ever be ok.

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><p><strong>Because despite Tadashi being a Really Good Guy, Hiro is his baby brother, his otouto, and grief can do savage things to the gentle mind.<strong>


	2. Bonus: Original Ending

**Oh my, I didn't expect such a positive response! Thank you all for your wonderful favorites and reviews!**

**I'm going to post the "original" ending to Five Alarm as a bonus for you all, you've really made my month :DD**

**It picks up off the line "For the first time, Tadashi burns", in case you're confused by the abrupt intro**

**Disclaimer: I don't own the copyrighted material within**

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><p><em>three alarm alt<em>

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><p>For the first time since the fire, Tadashi burns.<p>

He heads home and drags Baymax into the garage, wondering exactly how to take down the masked man. If Hiro were still alive, he'd turn Baymax into one of his fighting bots, and Tadashi is tempted to use his creation to destroy the thief of his brother's.

But he doesn't, when he sees Baymax hover by his side, scanning scanning scanning Tadashi's stitches, scars, and deteriorating mental health. He can't turn his creation into a weapon, not when all he wanted to do was help the world. Hiro...Hiro is beyond helping now, Hiro will never get to see Baymax save so many lives, but Tadashi can't stomach any more changes to his once bright future.

Instead, he upgrades Baymax to be the ultimate healthcare companion twenty times over. Armor to protect his vinyl skin, increased amounts of surgical tools and solutions, Tadashi blueprints a way to take Baymax into the sky and carry dozens of injured people on his back. It takes a week and his friends are worried that he's not eating enough and hiding secrets, but he's a charming man, he even gets Honey and Aunt Cass to relax.

Tadashi designs little details for himself; if Baymax can fly, Baymax can fly Tadashi into the heart of the microbots so that Tadashi may rip out the spine of Hiro's murderer, and therefore Tadashi needs a flight suit. And weapons too—blades clean and sharp, able to sever heads with a wrist flick and precise enough to carve out every drop of agony Tadashi's soul screams for in revenge. Baymax is concerned at the growing pile of hacked apart dummies, and Tadashi upgrades his scanner to make sure that the masked man will have nowhere to hide.

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><p><em>four alarm alt<em>

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><p>They fly, and Tadashi hollers into the air whipping past his face mask. Baymax takes him higher, Tadashi feels the power thrum beneath his hands and vibrate in the blades strapped to his back. San Fransokyo is beautiful from the ground and especially from the heavens, and Tadashi wants to cry because Hiro would've loved this.<p>

Tadashi lets himself imagine that Hiro were here, hands magnetized to Baymax so he won't fall off while he twists to stare at every new sight, new sound, new everything. His hands were the hands of a teenager, caught between childish fragility and adult bulk, yet Tadashi can only see tiny infant fingers curling around his thumb. Hiro was so small as a baby, small as a boy, small as a fourteen year old running into the science fair, smaller still as an urn of ashes at Tadashi's feet.

Tadashi cries and the tears are cold against his cheeks. Baymax inquires after his health and Tadashi is so relieved to have Baymax here, even above Aunt Cass and his friends because Baymax is his in a way that they aren't; maybe Hiro would've understood

and maybe Tadashi is tired of always wishing that he'd said "I love you" before Hiro died. When was the last time he'd explicitly said that out loud? Mother always said it, she said that there was never a bad time to let her sons know that kaasan loved them and Tadashi hopes that she's telling Hiro that right now, because Tadashi failed that part of being a big brother.

They rest on top of one of the "koi fish" turbine blimps, and Hiro used to sit on their father's shoulders and babble on about swimming in the sky. Tadashi's dopamine levels dip again and Baymax hugs him close to try and comfort him. Tadashi rests against Baymax and thanks him over and over, despite the robot not understanding why.

Maybe Hiro would've understood.

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><p><em>five alarm alt<em>

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><p>The masked man returns to destroy Krei's new building, and Tadashi is ready to fight him. He's not ready to see that it's Prof. Callaghan opening a portal to hell over San Fransokyo, and what is his mentor doing<p>

what has he done?

Tadashi flies Baymax in and they get their answers because Callaghan is a talkative man in his rage. Krei's teleportation portals killed Abigail, Tadashi's aerodyanamics TA and fellow chicken udon enthusiast and yet another person too far away to say goodbye to. Tadashi asks why Hiro is dead if Callaghan stole the microbots and started the fire and

Callaghan threw Hiro across the room with the microbots because Hiro almost took the neurotransmitter

Callaghan watched Hiro's head snap back against a concrete pillar, his scalp splitting and his eyes filled with so much pain and confusion

Callaghan used the microbots to save himself while Hiro crawled across burning wood and glass and metal to try and get back to his niisan

he caused Hiro's death and

didn't care

and Tadashi wants his head on a spike.

They fight, and they are outmatched by the microbots, but Callaghan is outmatched by Tadashi's unholy fury. Tadashi shreds through Hiro's inventions because they are tainted by the selfish grief of a murderer, and he gets close enough to swing his katana down and slice Callaghan's arm off.

He crumples and the mask tumbles away and Tadashi is giddy at the idea of skinning him alive. His soul bays for it. But Baymax distracts him because he can sense life in the deteriorating portal, and Abigail might be alive to render Callaghan's murder even more meaningless.

Tadashi is conflicted, but decides on holstering his katana in Callaghan's lower spine and gut; he's going to watch Tadashi bring his daughter back to life.

And she is alive, in a dimension filled with more colors than Tadashi knows. It's beautiful and dangerous and cold, so terribly cold, and he wonders if he's going to freeze to death and get tell Hiro that he loves him and he's just so so proud of his little brother because Hiro iswasiswas incredible.

Baymax flies Abigail's pod out just as the portal collapses in a sea of flames that makes Tadashi scream in terror because oh god, what if Baymax dies in the fire, what if Abigail dies in the fire, what if civilians die in the fire, what if even Krei dies in the fire

he is held by Baymax, muffling his wails into his armored chest as the pod hatch hisses and Abigail stutters into consciousness. Abigail is alive and Callaghan murdered Hiro for nothing, and it isn't fair. He wipes his eyes and turns on Callaghan, who coughs up blood and begs for time to see Abigail once last time before Tadashi kills him.

And Tadashi decides not to kill him, because the only murderer here is the pathetic man groveling at his feet and dishonoring Hiro's death with every second of his fear. "I'm not going to kill you," Tadashi leans down to whisper ever so gently into Callaghan's ear, "I'm going to tell Abigail about what you did. About how you killed a fourteen year old child to avenge a death that never happened."

Tadashi smiles and his heart burns, "She will hate you as long as she lives."

Callaghan cries out and struggles against the sword in his back, and Tadashi leaves him for the scattered policemen. Baymax carries Abigail to the paramedics and Tadashi turns to the crowd of spectators looking at him like Amaterasu rising from the clouds. Hiro once looked at him sorta like that, and Tadashi dislikes the half-imitation, all these eyes trained on his blades and samurai flight suit and tear stained cheeks. And his friends are there, Fred in awe because Tadashi is a hero and the others in concern because Tadashi is still without his Hiro and still so dangerous.

But Abigail's frightened eyes meet Tadashi's and maybe he'll never have Hiro back, not even if he turned back around and spent five years inventing new ways to kill Callaghan, but he has things to discuss and cry about with Abigail and Honey and Gogo and Wasabi and Fred and Mochi, and it's nice to not lose someone for a change.

Honey hugs Tadashi close, they all pile together against Baymax and Tadashi feels warmth spread back down into his shaking hands that still can't handle chopsticks.

"Do you require anything else?" Baymax is not Hiro, his friends are not Hiro, Abigail is not Hiro, Aunt Cass is not Hiro, and Tadashi is going to have to learn how to live with that. He's scared, and still bleeding, and it will never be as Tadashi wishes. But Hiro believed in him, and maybe Hiro would understand why Tadashi can't give up just yet; udon requires chopsticks just as much as charred bones do, and his bandages need to come off eventually.

Tadashi leans his head back against his creation for a glimpse of a purple koi fish swimming in the sky, and exhales, "More than anyone can do...but I think for now, I'm satisfied with my care."

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><p><strong>Yay happy ending! I think you all deserved that after the first edition, lol<strong>


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